What is the income distribution of super shoppers? Asupermarket super shopperis defined as a shopper for whom at least 70% of the items purchased were on sale or purchased with a coupon. In the following table, income units are in thousands of dollars, and each interval goes up to but does not include the given high value. The midpoints are given to the nearest thousand dollars.

Income range 5-15 15-25 25-35. 35-45 45-55 55 or more

Midpointx 10 20 30 40 50 60

Percent of Sup Sh 21%. 15% 20% 17% 18% 9%

(a)Using the income midpointsxand the percent of super shoppers, do we have a valid probability distribution? Explain.

(c)Compute the expected incomeof a super shopper (in thousands of dollars). (Enter a number. Round your answer to two decimal places.)

=thousands of dollars

(d)Compute the standard deviationfor the income of super shoppers (in thousands of dollars). (Enter a number. Round your answer to two decimal places.)

=thousands of dollars